Dictyostelium discoideum morphogenesis: the culmination

Stan Maree

University of Utrecht, The Netherlands
email: S.Maree@bio.uu.nl

Dictyostelium discoideum Morphogenesis: the Culmination Upon starvation, solitary amoebae of the cellular slime mould Dictyostelium discoideum aggregate and form a migrating multicellular slug. The slug migrates towards the soil surface, where migration halts and the whole process culminates in the formation of a fruiting body consisting of a globule of spores on a slender stalk. The movement during culmination has been likened to a ``reverse fountain'', whereby prestalk cells in the upper part form a stalk that moves downwards and anchors to the substratum, while prespore cells in the lower part move upwards to form the spore head. So far, however, no satisfactory explanation has been produced for this process. We have simulated the process of culmination using a hybrid cellular automata/partial differential equation model. In the model, individual cells are represented as a group of connected automata, i.e. the basic scale of the model is subcellular. With our model we have been able to reproduce the main features that occur during culmination, namely the straight downward elongation of the stalk, its anchoring to the substratum and the formation of the long thin stalk topped by the spore head. I will show that cyclic AMP signalling and differential adhesion, combined with cell differentiation and slime production, are sufficient to produce the morphogenetic cell movements which lead to culmination, and how the entire development is enacted by means of the above mentioned building blocks. This means that no global gradients or different modes of chemotaxis are needed to complete the culmination.